Field of the Invention
The present invention relates to a novel polymer compound having a sulfo group.
Description of the Related Art
A polymer containing a sulfo group has been used as a fuel cell or a dopant polymer for a conductive polymer. As a material for a fuel cell, vinyl perfluoroalkyl ether sulfonic acid represented by Registered Trademark of Nafion has widely been used, and as a dopant polymer for a conductive polymer, a polymer of vinyl sulfonic acid or styrene sulfonic acid has widely been used (Patent Document 1).
The vinyl perfluoroalkyl ether sulfonic acid has chemically high stability and excellent durability, but the glass transition point thereof is low, so that there is a problem that when a fuel cell using it is exposed to high temperature, the polymer causes heat flow whereby ion conductivity thereof is lowered. A super strongly acidic polymer having a sulfo group an α-position of which has been fluorinated is effective for heightening ion conductivity, but a material having high glass transition point and chemical stability with high ion conductivity has not yet been found out.
Also, a conductive polymer having a conjugated double bond such as a polythiophene, a polyaniline, a polypyrrole, etc., does not show conductivity itself, but conductivity thereof is expressed by doping therein a strong acid such as sulfonic acid, etc. As the dopant, polystyrene sulfonic acid (PSS) has most frequently been used. This is because conductivity becomes the highest by doping the PSS.
PSS is a water-soluble resin, and is difficultly dissolved in an organic solvent. Accordingly a polythiophene which uses the PSS as a dopant is also water-soluble.
The polythiophene which uses the PSS as a dopant is highly conductive and highly transparent so that it has been expected to be a conductive film for an organic EL lighting substituting for ITO (indium-tin oxide. However, a luminous body of the organic EL chemically changes by moisture and stops to emit a light. That is, when a conductive film comprising a water-soluble resin is used for an organic EL, there is a problem that an emission lifetime of the organic EL becomes short due to the resin containing water.